Electric tubular heater



July 7, 1953 A. P. cHARBoNNl-:AU ETAL Re. 23,679

ELECTRIC TUBULAR HEATER TERMINAL sEAL originaLFiled-Jan. a. 194e l 5mm/M186 @qm/vm FUSION WELD lll I. II

Reissued July 7, 1953 ELECTRIC TUBULAR HEATER TERMINAL SEAL Allan P. Charbonneau and Edwin W. Seeger, Wauwatosa, Wis., assignors to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation oi' Dela- Ware original No. 2,489,998, dma November 29, 1949, Serial No. 1,146, January 8, 1948. Application for reissue August 24, 1950, Serial No. 181,191

' Matter enclosed in heavy brackets :I appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

'l Claims.

This invention relates to electric heaters and more particularly to an improved method of and means for sealing terminals of heaters having tubular enclosing sheaths.

An object. of the present invention is to provide for making a highly satisfactory terminal seal for tubular sheathed heaters in a simple and expeditious manner.

Another object is to provide a terminal seal which is impervious to moisture and of a nonbreakable character.

Another object is to provide a terminal seal of the aforementioned character without the application' of heat or introduction of fusible sealing materials.

Other'objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate an embodiment of the invention which will now be described.

In the drawings;

Figure 1 is a View in longitudinal section of a portion of a tubular type heater prior to the application of a terminal seal.

Fig. 2 is like Fig. 1, but shows the terminal seal in a completed state, and

Fig. 3 is like Fig. 2, but modified in respect of the terminal seal retaining member.

Referring to Fig. 1, it shows a tubular type electric heater comprising a helical resistor 5 which is embedded in a compacted mass of refractory insulating material E and incased by a tubular metal sheath 1 of any preferred cross sectional form, The resistor 5 is connected in any preferred manner to a terminal lead 8 which extends outwardly of the sheath 1. The sheath adjacent its end is unfilled and provides -a recess 9 to receive the terminal seal.

Prior to applying the terminal seal, it is assumed that the heater has been worked as by swaging to the desired cross sectional form and dimensions.

A plug I0 composed of silicone rubber of elastic character, such as, for example, Dow Corning Silastic No. 180, is used for eiecting a terminal seal. match the cross sectional form of the recess 9 but with slightly smaller dimensions to facilitate its insertion within recess 9. It is also provided with a central longitudinal perforation I I to provide clearance for terminal lead Il. The length of plug I0 is preferably somewhat in excess of the depth ot recess 9.

To effect the terminal seal, plug IIJ is slipped onto terminal lead 8 and is inserted into recess 9 Preferably plug I0 is externally formed tol Cil so that its inner end engages the insulating material 6. Then a locking member I2, which in one preferred form is a blade-like terminal device shown in Fig. 2, is attached to the extended end of terminal lead 8 as by fusion welding. To afford proper sealing action by the plug I0 it is necessary that member I2, during and following its attachment to the terminal lead B in any preferred manner compress the plug I0 inwardly of the recess 9 to effect longitudinal compression of the plug. Such compression of the plug I0 provides for lateral expansion of the same within recess 9 to effect intimate and tightly tting engagement of the plug with the inner walls of sheath 'l and with the terminal lead 8.

As shown in Fig. 2, a washer I3 is preferably interposed between the adjacent ends of plug Ill and member I2 to insure that when the latter is attached to terminal lead 8 it will exert pressure on plug II!y substantiallyv uniformly about the cuter end of the latter. However, washer I3 may be dispensed with as desired when other preferred locking members or terminal devices are used which are provided with abutting end portions that substantially overlie the end of the plug; such as for example another preferred type of terminal device I4 shown in Fig. 3.

If the terminal seal has been effected as hereinbefore described a finished -terminal such as shown in Figs. 2 and 3 will be had. The terminal seal will be moisture impervious and of a non-breakable character. The use of a silicone rubber plug as the sealing medium insures that the seal will not disintegrate unless the tempera- 500 Fahrenheit. The terminal end temperatures of properly designed and constructed tubular sheathed heaters such as used in the cooking art vare substantially below 500 Fahrenheit even lwhen subjected to their maximum rated wattages. The danger of seal disintegration due to heat is therefore remote.

It will be apparent that the terminal seal described herein has numerous advantages. The use of fusible sealing materials is obviated, and several steps heretofore used in providing a finished terminal seal are eliminated. Consequently there is a saving in time and cost. Be-

cause of the elastic character of the seal it is not subject to breakage which is ordinarily associated with many types of terminal seals heretofore used.

What we claim as new and desire to secure by Letters Patent is:

[1. The method of sealing the terminal end of an electric heater wherein a resistor enclosed in an open end tubular sheath is embedded in insulation at a distance from the end of the sheath to leave the sheath with an open end recess. and wherein the resistor has a terminal portion projecting through such recess to a point beyond the sheath, comprising the step of inserting a perforated heat resistant plug oi elastic character into the open end recess of said heater, compressing said plug inwardly of said recess to cause lateral expansion of said plug for engagement with the inner walls of said sheath and with said terminal portion of said resistor. and

locking a member to said terminal portion of said resistor to retain said plug in compressed condition] [2. The method of sealing the terminal end of an electric heater wherein a resistor enclosed in an open end tubular sheath is embedded i'n insulation at a distance from the end of the sheath to leave .the sheath with an open end recess, and wherein the resistor has a terminal portion projecting through such recess to a point beyond the sheath, comprising the steps of slipping onto the terminal portion of said resistor a perforated silicone rubber plug of elastic character, inserting said plug into the open end recess of said heater, compressing said plug inwardly of said recess to cause lateral expansion of said plug ior engagement with the inner walls of said sheath and with said terminal portion of said resistor, and locking a member to said terminal portion of said resistor to retain said plug in compressed condition] [3. The combination with a tubular heater comprising a resistor having a terminal portion,

an open end tubular sheath surrounding said resistor and also its terminal `portion in part, and

- insulation in said sheath retaining said resistor in spaced relation to said sheath, said insulation terminating at a distance from the end of said sheath leaving said sheath with an open end recess through which said terminal portion projects. of a perforated elastic plug formed of heat resistant material compressed in situ to tightly engage said insulation, the inner walls of said sheath and the terminal yportion of said resistor projecting through said recess, and a member locked to said terminal portion of said resistor to maintain said plug in such compressed state] [4. The combination with a tubular heater comprising a resistor having a terminal portion, an open end tubular sheath surrounding said resistor and also its terminal portion in part, and insulation in said sheath retaining said resistor in spaced relation to said sheath, said insulation terminating at -a distance from the end of said sheath, leaving said sheath with an open end recess through which said terminal portion projects. of a perforated silicone rubber plug of elastic character compressed in situ to tightly into the open end recess of said heater, compressing said plug inwardly of said recess to cause lateral expansion' of said plug forengagement with the inner wall of said sheath and with the terminal portion of said resistor, and locking a member to said terminal portion of said resistor to retain said plug in compressed condition.

6. The method of sealing the terminal end of an electric heater wherein a resistor enclosed in an open end tubular sheath is embedded in insulation at a distance from the end of the sheath to leave the sheath with an open end recess. and wherein the resistor has a terminal portion projecting through such recess to a point beyond the sheath, comprising the steps of slipping onto the terminal portion of said resistor a perforated silicone rubber plug of elastic character, inserting said plug inta the open end recess of said heater, compressing said plug inwardly o! said-recess to cause lateral expansion of said plug for engagement with the inner wall of said sheath and with said 'terminalportion of said resistor. and, locking a member to said terminal portion of said resistor to retain said plug in compressed condition.

7. The combination with a tubular heater comprising a resistor having a terminal member, an open end tubular sheath member surrounding said resistor and also its said terminal member in part and a compacted mass of refractory insulating material in said sheath member wherein the resistor and a portion of the terminal member are embedded in spaced relation to said sheath member, said insulating material terminating'at a distance from the end of said sheath member leaving said sheath member with an open end re-V cess through which said terminal member projects, of a perforated elastic plug formed of heat resistant material compressed in situ to tightly engage said insulating material, the inner wall of said sheath and the portion of said terminal member projecting through said recess, and a member locked to said terminal member to maintain saidplug in such compressed state.

8. The combination with a tubular heater comprising a resistor having a terminal member, an open end tubular sheath member surrounding said resistor and also its said terminal member in part and a compacted mass of refractory insulating material in said sheath member wherein the resistor and a portion of the terminal member are embedded in spaced relation to said sheath member, said insulating material terminating at a distance from the end of said sheath engage said insulation, the inner walls of said sheath and the terminal portion of said resistor projecting through said recess, and a member locked to said terminal portion o! said resistor to maintain said plug in such compressed state] 5. The method o] sealing the terminal end of an electric heater wherein a resistor enclosed in an open end tubular sheath is embedded in insulation at a distance from the end of ythe sheath to leave the sheath with an open end recess,l and wherein the resistor has a terminal portion proiecting through such recess to a point beyond the sheath comprising the steps of inserting a perforated heat resistant plug of elastic character in part and a compacted mass of refractory insulating material in said sheath member wherein the resistor and a portion of the terminal member are embedded in spaced relation to said sheath member, said insulating material terminating at a distance from the |`end of said sheath member leaving said sheath member with an open end recess through which said terminal member projects, of a perforated elastic plug formed of heat resistant material bearing against said insulating material and compressed in situ for annular sealing with the peripheral'surface of said terminal member and with the inner peripheral surface of said sheath member, at least one of said members having means to retain said plug in compressed state and toflock it against displacement axially.

10. The combination with a tubular heater comprising a resistor having a terminal member, an open end tubular sheath member surrounding said resistor and also its said terminal member in part and a compacted mass of refractory insulating material in said sheath member wherein the resistor and a portion of the terminal member are embedded in spaced relation to said sheath member, said insulating material terminating at a distance from the end of said sheath member leaving said sheath member with an open end recess through which said terminal member projects, of a perforated silicone rubber plug of elastic character bearing against said insulating material and compressed in situ for annular sealing with the peripheral surface of said terminal member and the inner peripheral surface of said sheath member, at least one of said members having means to retain said plug in compressed state and to lock it against displacement axially.

11. An electric heater comprising a resistor, a sheath in general surrounding said resistor and spaced from said resistor, said sheath being provided with at least one terminal opening and said heater comprising a terminal for said resistor located at said opening and spaced from said lsheath, and closure means for said opening. permitting electrical connection to said terminal and gagement with a corresponding portion of the peripheral surface of said opening, and means so holding said member.

' l ALLAN P. CHARBONNEAU.

EDWIN W. SEEGER.

References Cited in the 111e 0I this patent or the original patent UNITED STATES PATENTS Number Name Date 2,003,175 Daly May 28, 1935 2,369,045 Hampton et al. Feb. 6, 1945 2,375,058 Wiegand May 1, 1945 2.397.568 Seaman Apr. 2, 1946 2,428,053 Vasileil' Sept. 30, 1947 2,460,795 Warrick Feb. 1,V 1949 FOREIGN PATENTS Number Country Date Great Britain Nov. 9, 1938 OTHER REFERENCES Knight, ssnliwrmsxl oct. 1945, pp. 1069-73 of'- Materials and Methods. y

Silicones, April 22, 1946, pp. 121-122 o! SteeL 

